Anything above about a C-30 is getting into "real truck" territory. That includes the frame, the running gear, wheels, tires, brakes and other stuff that's intended to haul heavy loads at moderate speeds. It also gets into license plates and insurance rates that aren't very friendly to a Cowboy Cadillac daily driver. Unless your local DMV has some sort of accomodation for project vehicles that aren't used for their original purposes, licencing and insuring it could turn into a bottomless money pit. Even with your photo blown up several sizes, it's impossible to tell if the truck is running the Firestone RH-5 "widowmaker" wheels. If so, your first concern will be a couple of thousand dollars' worth of legal wheels and tires. Smaller, more modern wheels and suspension will look completely out of place on a big rig. Give some thought to what you intend to do with the finished project, and proceed accordingly.
Jerry
Between Arizona's lenient registration laws and Hagerty for insurance, no real issues with any of the paperwork stuff. The wheels are not the widowmakers. Already spent that couple thousand dollars...wheels are solid and all six tires are brand new.
If I did the chassis swap I would use some steel wheels and appropriately sized tires.
Leaning towards not messing with it though, like Dingo suggested.
